JP7197413B2 - steering control system - Google Patents

Description

The present invention relates to a steering control system, and more particularly to a steering control system for a steer-by-wire vehicle.

Patent Literature 1 discloses a technique related to a steering control device that performs processing for suppressing steering operation so that the steering angle exceeds an upper limit value. In this technique, when the maximum value of the turning angle of the wheels or the steering angle of the steering is greater than or equal to the limit start threshold, the reaction force actuator is operated to further increase the steering angle. The limiting reaction force for limiting is rapidly increased.

Further, Patent Literature 2 discloses a technique related to a steering control device capable of adjusting a steering angle ratio characteristic representing the relationship between the steering angle of the steering wheel and the steering angle of the steered wheels. In this technique, at least two characteristics, ie, the steering angle ratio characteristic during running and the steering angle characteristic during stopping, are set as the steering angle ratio characteristic.

JP 2018-047784 A JP 2015-123864 A

In a configuration that adjusts the steering angle ratio characteristic according to changes in the state of the vehicle, as in the technique of Patent Document 2, it is possible to optimize the steering angle ratio characteristic according to the state of the vehicle. However, if the steering angle ratio characteristic changes, the steering angle (steering end) of the steering corresponding to the steering end at which the steering angle becomes maximum changes. For this reason, if the technique of Patent Document 2 is applied to a configuration in which the reaction torque is rapidly increased at the steering end as in the technique of Patent Document 1, the vehicle that is being steered at the end of the steering will react when the state of the vehicle changes. There is a risk that the force torque will suddenly change, and the driver will feel a sense of incongruity in steering. As described above, in the steering control of a steer-by-wire type vehicle in which the steering angle ratio characteristic can be adjusted according to the state of the vehicle, there is a problem in controlling the reaction torque when the state of the vehicle changes at the steering end.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and is a steering control that can suppress a sudden change in reaction torque when the steering angle of a steer-by-wire vehicle is steered to the steering end. The purpose is to provide a system.

In order to solve the above problems, a first invention is applied to a steering control system for a steer-by-wire vehicle. The steering control system includes a steering device that steers the wheels of the vehicle by operating a steering motor, a reaction force generating device that applies a reaction torque to the steering of the vehicle by operating a reaction force motor, and a vehicle speed . and a control device for calculating the steering angle of the wheels for controlling the steering device and the reaction force torque for controlling the reaction force generating device. The control device includes a steering angle calculation unit that calculates a turning angle corresponding to the steering angle based on the first characteristic, and a reaction torque calculation unit that calculates a reaction torque corresponding to the steering angle based on the second characteristic. and Here, the first characteristic is a characteristic representing the relationship between the magnitude of the steering angle and the steering angle of the steering wheel, and the second characteristic is a characteristic representing the magnitude of the reaction torque relative to the steering angle. The first characteristic and the second characteristic are configured to be adjustable according to the vehicle speed . In response to the vehicle speed changing from the first state to the second state, the steering angle calculation unit changes the first characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state. It is configured. Then, when the steering angle is steered to the steering end corresponding to the upper limit of the steering angle, the reaction force torque calculation unit changes the second characteristic to the first state when the vehicle speed changes from the first state to the second state. It is configured to maintain the characteristics corresponding to the state.

The second invention has the following features in addition to the first invention.
After the vehicle speed changes from the first state to the second state at the steering end, the reaction force torque calculation unit changes the second characteristic to correspond to the first state when the steering angle is returned to the predetermined steering angle in the third state. It is configured to change from a characteristic to a characteristic corresponding to the third state.

A third invention is applied to a steering control system for a steer-by-wire vehicle in order to solve the above problems. The steering control system includes a steering device that steers the wheels of the vehicle by operating a steering motor, a reaction force generating device that applies a reaction torque to the steering of the vehicle by operating a reaction force motor, and a vehicle speed . and a control device for calculating the steering angle of the wheels for controlling the steering device and the reaction force torque for controlling the reaction force generating device. The control device includes a steering angle calculation unit that calculates a turning angle corresponding to the steering angle based on the first characteristic, and a reaction torque calculation unit that calculates a reaction torque corresponding to the steering angle based on the second characteristic. and Here, the first characteristic is a characteristic representing the relationship between the magnitude of the steering angle and the steering angle of the steering wheel, and the second characteristic is a characteristic representing the magnitude of the reaction torque relative to the steering angle. The first characteristic and the second characteristic are configured to be adjustable according to the vehicle speed . In response to the vehicle speed changing from the first state to the second state, the steering angle calculation unit changes the first characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state. It is configured. Then, when the steering angle is steered to the steering end corresponding to the upper limit of the turning angle, the reaction force torque calculating section calculates the speed of change of the vehicle speed when the vehicle speed changes from the first state to the second state. It is configured to change the second characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state by a slow change speed.

A fourth invention has the following features in addition to any one of the first to third inventions.
The second state has a higher vehicle speed than the first state. The steering angle calculation unit is configured to change the first characteristic so that the magnitude of the steering angle with respect to the steering angle decreases when the vehicle speed changes from the first state to the second state at the steering end. ing.

A fifth invention has the following features in addition to any one of the first to third inventions.
The second state has a lower vehicle speed than the first state. The steering angle calculation unit is configured to change the first characteristic so that the magnitude of the steering angle with respect to the steering angle increases when the vehicle speed changes from the first state to the second state at the steering end. ing.

According to the steering control system of the first invention, even when the vehicle speed changes from the first state to the second state at the steering end and the first characteristic changes, the second characteristic remains in the first state. Corresponding properties are retained. As a result, the reaction torque can be maintained even when the steering end is changed, so it is possible to suppress the sudden change in the steering angle of the steering wheel and eliminate the discomfort of the driver.

According to the steering control system of the second invention, when the steering angle is returned to the predetermined steering angle in the third state after the vehicle speed changes from the first state to the second state at the steering end, the second characteristic The property corresponding to one state is changed to the property corresponding to a third state. The second characteristic is that the smaller the steering angle, the smaller the difference in the reaction torque according to the vehicle speed . Therefore, according to the present invention, it is possible to make the second characteristic follow the characteristic corresponding to the vehicle speed while suppressing a sudden change in the reaction torque.

According to the steering control system of the third invention, even when the vehicle speed of the vehicle changes from the first state to the second state at the steering end and the first characteristic changes, the second characteristic is the change in the state. The characteristic corresponding to the first state changes to the characteristic corresponding to the second state by a change speed slower than the speed. As a result, even when the vehicle speed changes and the steering end changes, the reaction torque fluctuates accordingly, so that the driver can turn the steering wheel in or out without discomfort.

According to the fourth invention, when the vehicle accelerates at the steering end, it is possible to prevent the steering angle from further cutting.

According to the fifth invention, when the vehicle decelerates at the steering end, it is possible to prevent the steering angle from being abruptly turned back.

1 is a block diagram schematically showing a configuration example of a steering control system according to an embodiment; FIG. 3 is a block diagram for explaining functions of a control device; FIG. It is a figure which shows an example of the 1st characteristic which the control apparatus has memorize|stored. It is a figure which shows an example of the 2nd characteristic which the control apparatus memorize|stores. FIG. 4 is a diagram for explaining a problem of reaction torque control; It is a figure for demonstrating reaction force torque adjustment processing. 4 is a time chart showing changes in vehicle speed and steering angle in reaction force torque adjustment processing; 4 is a flowchart showing an outline of processing by the steering control system according to Embodiment 1; FIG. 10 is a diagram for explaining reaction force torque adjustment processing according to the second embodiment; FIG. 9 is a time chart showing changes in vehicle speed and steering angle in the reaction force torque adjustment process of Embodiment 2; 9 is a flowchart showing an overview of processing by a steering control system according to Embodiment 2;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, when referring to numbers such as the number, quantity, amount, range, etc. of each element in the embodiments shown below, unless otherwise specified or clearly specified by the number in principle, the reference The present invention is not limited to this number. Also, the structures, steps, etc. described in the embodiments shown below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

1. Embodiment 1.
1-1. Steering Control System FIG. 1 is a block diagram schematically showing a configuration example of a steering control system according to the present embodiment. A steering control system 1 is mounted on a vehicle and steers wheels WH of the vehicle in a steer-by-wire manner. That is, the steering control system 1 implements a steer-by-wire vehicle.

In the example shown in FIG. 1, the steering control system 1 includes a steering wheel (steering) 10, a steering shaft 20, a reaction force generator 30, a steering device 40, a group of sensors 51 to 53, and a control device 100. .

The steering wheel 10 is an operation member used by the driver for steering. The steering shaft 20 is connected to the steering wheel 10 and rotates together with the steering wheel 10 .

The reaction force generator 30 sends reaction force motor state information STR indicating the state of the reaction force motor 31 to the control device 100 . For example, the reaction motor state information STR indicates the drive voltage, drive current, rotation angle, rotation speed, temperature, etc. of the reaction motor 31 .

The steering device 40 steers the wheels WH. Specifically, the steering device 40 includes a steering motor 41 , a speed reducer 42 and a steering shaft 43 . A rotor of the steering motor 41 is connected to a steering shaft 43 via a reduction gear 42 . The steered shaft 43 is connected to the wheels WH. When the steering motor 41 rotates, the rotary motion is converted into linear motion of the steering shaft 43, thereby steering the wheels WH. That is, the wheels WH can be steered by the operation of the steering motor 41 . The operation of the steering motor 41 is steered by the control device 100 .

The steering device 40 sends steering motor state information STM indicating the state of the steering motor 41 to the control device 100 . For example, the steering motor state information STM indicates the drive voltage, drive current, rotation angle, rotation speed, temperature, etc. of the steering motor 41 .

The steering device 40 is mechanically separated from the steering wheel 10 and the reaction force generating device 30 on the steering side.

A steering angle sensor 51 detects a steering angle θ that is the rotation angle of the steering wheel 10 . The steering angle sensor 51 sends information on the detected steering angle θ to the control device 100 .

A steering torque sensor 52 detects a steering torque TS applied to the steering shaft 20 . The steering torque sensor 52 sends information on the detected steering torque TS to the control device 100 .

A vehicle speed sensor 53 detects a vehicle speed V, which is the speed of the vehicle. Vehicle speed sensor 53 sends information on detected vehicle speed V to control device 100 . A wheel speed sensor may be used instead of the vehicle speed sensor 53, and the vehicle speed V may be calculated from the rotation speed of each wheel.

Control device 100 controls the steering control system according to the present embodiment. The controller 100 includes a microcomputer with a processor 102 , memory 104 and an input/output interface 106 . This microcomputer is also called an ECU (Electronic Control Unit). Processing by the control device 100 is executed by the processor 102 executing the control program stored in the memory 104 .

1-2. Configuration of Control Device FIG. 2 is a block diagram for explaining the functions of the control device. The control device 100 controls the steering of the wheels WH by controlling the steering motor 41 according to the rotation (steering) of the steering wheel 10 . This control is also called "steering angle control". Further, the control device 100 controls the reaction force torque TR applied to the steering wheel 10 by controlling the reaction force motor 31 according to the rotation (steering) of the steering wheel 10 . This control is also called "reaction torque control". The control device 100 includes a steering angle calculator 110, a steering angle controller 120, a reaction torque calculator 130, and a reaction torque as functional blocks for realizing steering angle control and reaction torque control. A control unit 140 is provided.

A steering angle calculator 110 receives inputs of the steering angle θ and the vehicle speed V and outputs a target steering angle θwt. The steering angle calculator 110 stores a first characteristic representing the relationship between the steering angle θw and the steering angle θ for each state of the vehicle. The state of the vehicle here is the vehicle speed V, for example. FIG. 3 is a diagram showing an example of first characteristics stored in the control device. In this figure, the characteristics at vehicle speed A and the characteristics at vehicle speed B, which is higher than vehicle speed A, are illustrated. As shown in this figure, the first characteristic is related such that the larger the vehicle speed V, the smaller the steering angle θw with respect to the steering angle θ. That is, the first characteristic is configured to be adjustable according to the vehicle speed V as the state of the vehicle. According to such a first characteristic, as the vehicle speed V increases, the steering angle θmax (steering end) corresponding to the turning end θwmax at which the turning angle θw becomes maximum (upper limit) is set to a larger angle. That is, the steering angle (steering end) θBmax corresponding to the steering end θwmax at vehicle speed B is set to be greater than the steering angle (steering end) θAmax corresponding to the steering end θwmax at vehicle speed A. be. The steering angle calculator 110 calculates a steering angle θw corresponding to the input steering angle θ and vehicle speed V from the first characteristic, and outputs it as a target steering angle θwt. The calculated target steering angle θwt is output to steering angle control section 120 .

The turning angle control unit 120 controls the turning motor 41 so that the turning angle of the wheels WH becomes the target turning angle θwt. More specifically, the steering angle control section 120 generates the current control signal S1 for driving the steering motor 41 based on the rotation angle of the steering motor 41 and the target steering angle θwt. The steering motor 41 is driven according to the current control signal S1, and the rotation of the steering motor 41 steers the wheels WH.

Reaction torque calculator 130 receives input of steering angle θ and vehicle speed V and outputs target reaction torque TRt. The reaction torque calculator 130 stores a second characteristic representing the relationship between the magnitude of the reaction torque TR and the steering angle θ for each state of the vehicle. The state of the vehicle here is the vehicle speed V, for example. FIG. 4 is a diagram showing an example of second characteristics stored in the control device. In this figure, the characteristics at vehicle speed A and the characteristics at vehicle speed B, which is higher than vehicle speed A, are illustrated. As shown in this figure, the second characteristic is related such that the larger the vehicle speed, the smaller the magnitude of the reaction torque TR with respect to the steering angle θ. That is, the second characteristic is configured to be adjustable according to the vehicle speed V as the state of the vehicle. According to the second characteristic, as the vehicle speed increases, the steering end θmax for generating the end reaction force TRmax, which is the reaction force corresponding to the steering end θwmax, is set at a larger angle. That is, the steering end θBmax corresponding to the end reaction force TRmax at the vehicle speed B is set to be larger than the steering end θAmax corresponding to the end reaction force TRmax at the vehicle speed A. The reaction torque calculator 130 calculates a reaction torque TR corresponding to the input steering angle θ and vehicle speed V from the second characteristic, and outputs it as a target reaction torque TRt. The calculated target reaction torque TRt is output to reaction torque control section 140 .

The reaction torque control unit 140 controls the reaction motor 31 so as to generate the target reaction torque TRt. More specifically, the reaction torque control unit 140 generates a current control signal for driving the reaction motor 31 based on the calculated target reaction torque TRt, the rotation angle of the reaction motor 31, the steering torque TS, and the like. Generate S2. The reaction motor 31 is driven according to the current control signal S2, thereby generating reaction torque TR.

Note that the control device 100 includes a first control device including a turning angle calculation section 110 and a turning angle control section 120 for realizing turning angle control, and a reaction torque calculation for realizing reaction torque control. A second controller consisting of a section 130 and a reaction torque control section 140 may be included separately. In this case, the first control device and the second control device are connected so as to be able to communicate with each other, and exchange necessary information with each other.

1-3. Reaction Force Torque Adjustment Processing When the reaction force torque control described above is executed together with the turning angle control, the following problems occur. FIG. 5 is a diagram for explaining a problem of reaction torque control. Consider the case where the vehicle is steered to the steering end θAmax at a vehicle speed A as shown in this figure. In this case, when the state of the vehicle changes from vehicle speed A as the first state to vehicle speed B (>vehicle speed A) as the second state, the first characteristic in steering angle control changes in response to the change in vehicle speed. increases the steering angle corresponding to the steering end. Further, when the vehicle state changes from vehicle speed A to vehicle speed B, the reaction force corresponding to the steering angle θAmax decreases due to the change in the second characteristic in the reaction force torque control. As a result, the steering wheel 10 suddenly turns to the new steering end θBmax, which causes a problem that the driver feels uncomfortable. It should be noted that the problem of abrupt changes in the reaction torque at the steering end can occur not only when the vehicle speed increases, but also when the vehicle speed decreases.

Therefore, the steering control system 1 of the present embodiment executes "reaction torque adjustment processing" for adjusting the magnitude of the reaction torque as necessary. The reaction force torque adjustment process is a process for suppressing a sudden change in the steering angle that is not intended by the driver. For example, when the vehicle speed changes while the steering wheel 10 of the vehicle is being steered to the steering end, reaction force torque adjustment processing is executed to suppress sudden changes in the steering angle.

FIG. 6 is a diagram for explaining the reaction torque adjustment process. FIG. 7 is a time chart showing changes in vehicle speed and steering angle in the reaction torque adjustment process. The reaction torque adjustment process is executed in reaction torque calculation section 130 of control device 100 . The examples shown in FIGS. 6 and 7 show the case where the vehicle traveling at vehicle speed A (first state) is accelerated at time t2 and then travels at vehicle speed B (second state). First, when the steering of the steering wheel 10 is started at time t0, the steering is turned to the steering end θAmax at the vehicle speed A at time t1, and the steering is maintained until time t2. During the period from time t0 to time t2, the reaction torque calculation unit 130 uses the second characteristic corresponding to the vehicle speed A to calculate the reaction torque TR corresponding to the input steering angle θ.

On the other hand, when the vehicle speed changes from vehicle speed A to vehicle speed B with the steering angle θ at the steering end θAmax at time t2, the reaction force torque calculation unit 130 applies the subsequent second characteristic to the vehicle speed B. The characteristics corresponding to the vehicle speed A are maintained as they are without switching to the characteristics that have been set. Thus, the steering angle θ is maintained at the steering angle θAmax corresponding to the vehicle speed A even when the steering end changes from θAmax to θBmax due to a change in vehicle speed. As a result, it is possible to suppress the cutting of the steering wheel 10 due to a sudden change in the reaction torque, so that the driver's sense of discomfort is reduced.

After that, when the steering wheel 10 is turned back by the driver at time t3, the reaction torque also decreases accordingly. Here, the reaction torque calculator 130 continues to use the second characteristic corresponding to the vehicle speed A to calculate the reaction torque TR corresponding to the input steering angle θ.

Here, the second characteristic is that the smaller the steering angle, the smaller the difference in reaction torque due to the difference in vehicle speed. Therefore, when the steering angle θ is turned back to the predetermined steering angle θth at time t4, the reaction force torque calculation unit 130 sets the second characteristic to the characteristic corresponding to the state of the vehicle at that time (third state). (here, characteristics corresponding to vehicle speed B). The predetermined steering angle θth here is preferably set to a steering angle at which a step in reaction torque generated before and after switching of the second characteristic is permissible from the viewpoint of drivability. According to such reaction torque adjustment processing, it is possible to effectively suppress a sudden change in the reaction torque at the end of steering.

1-4. Example of Processing by Steering Control System FIG. 8 is a flowchart showing an overview of processing by the steering control system according to the first embodiment. The processing shown in FIG. 8 is repeatedly executed in each constant cycle in the reaction force torque calculation section 130 of the control device 100 .

In the process of step S100 shown in FIG. 8, it is determined whether or not the "steering end condition" is satisfied. The steering end condition here is a condition for determining whether or not the steering angle has reached the steering end. It can be determined by whether or not the steering end θmax has been reached. As a result of the determination, if the steering end condition is not satisfied, the process proceeds to step S108, which will be described later. On the other hand, if it is determined that the steering end condition is established, the process proceeds to the next step S102.

In the process of step S102, it is determined whether or not the vehicle speed has changed. As a result, if the vehicle speed has not changed, the process proceeds to step S108, which will be described later. On the other hand, if the vehicle speed has changed, the process proceeds to the next step S104.

In the process of step S104, the target reaction torque TRt corresponding to the input steering angle θ is calculated using the second characteristic corresponding to the vehicle speed before change. In the processing of the next step S106, it is determined whether or not the "steering return condition" is satisfied. The steering return condition is a condition determined by whether or not the steering angle θ is returned to a predetermined steering angle θth or less. As a result, if the steering return condition is not satisfied, the process returns to step S104 to calculate the reaction force torque. On the other hand, if it is recognized that the steering return condition is established, the process proceeds to the next step S108.

In the process of step S108, the second characteristic corresponding to the current vehicle speed V is used to calculate the target reaction torque TRt corresponding to the input steering angle θ. When the process of step S108 is completed, this routine ends.

As described above, according to the reaction force torque adjustment process shown in FIG. 8, it is possible to suppress abrupt fluctuations in the reaction force torque, which is a problem when the vehicle speed changes at the end of steering. As a result, it is possible to prevent the steering wheel from being abruptly moved, so that the driver's sense of discomfort is reduced.

1-5. Modifications The steering control system 1 of the first embodiment described above may be modified as follows.

The reaction force torque adjustment process may be applied not only when the vehicle speed changes at the steering end, but also when the vehicle state changes. For example, the reaction force torque adjustment process may be configured to be executed when the yaw rate or lateral acceleration of the vehicle changes at the steering end. In this case, the first characteristic and the second characteristic may be defined for each vehicle state (yaw rate, lateral acceleration). The configuration of this modified example can also be applied to a steering control system according to a second embodiment, which will be described later.

The reaction force torque adjustment process may be applied not only when the change in vehicle speed at the steering end is acceleration but also when it is deceleration. In this case, it is suppressed that the steering wheel 10 is turned back due to a sudden increase in the reaction torque at the steering end. The configuration of this modified example can also be applied to a steering control system according to a second embodiment, which will be described later.

2. Embodiment 2.
2-1. Features of Embodiment 2 The steering control system of Embodiment 2 has a reaction torque that gradually decreases when the vehicle speed changes (accelerates) from vehicle speed A to vehicle speed B (>vehicle speed A) at the steering end. It is characterized by performing adjustment processing. The configuration of the steering control system of the second embodiment is the same as the configuration of the steering control system 1 of the first embodiment. Also, the basic concept of steering angle control and reaction torque control is the same as in the first embodiment. Descriptions overlapping with those of the first embodiment are omitted as appropriate.

FIG. 9 is a diagram for explaining reaction force torque adjustment processing according to the second embodiment. FIG. 10 is a time chart showing changes in vehicle speed and steering angle in the reaction torque adjustment process of the second embodiment. The reaction force torque adjustment process executed in the steering control system of the second embodiment is executed in reaction force torque calculation section 130 of control device 100 . The examples shown in FIGS. 9 and 10 show the case where the vehicle traveling at vehicle speed A (first state) is accelerated at time t2 and then travels at vehicle speed B (second state). First, when the steering of the steering wheel 10 is started at time t0, the steering is turned to the steering end θAmax at the vehicle speed A at time t1, and the steering is maintained until time t2. During the period from time t0 to time t2, the reaction torque calculation unit 130 uses the second characteristic corresponding to the vehicle speed A to calculate the reaction torque TR corresponding to the input steering angle θ.

On the other hand, when the vehicle speed changes from vehicle speed A to vehicle speed B with the steering angle θ set to the steering end θAmax at time t2, the reaction torque calculation unit 130 calculates the vehicle speed used to calculate the reaction torque as follows: The actual vehicle speed A is changed to the vehicle speed B more slowly than the change speed. For example, the reaction force torque calculation unit 130 applies a predetermined smoothing process to the change from the vehicle speed A to the vehicle speed B, thereby making the change in the vehicle speed used for calculation slower than the actual speed change. In addition, the reaction force torque calculation unit 130 can also make the change in the vehicle speed used for calculation slower than the actual speed change by guarding the speed of change from the vehicle speed A to the vehicle speed B with a predetermined upper limit value. As a result, it is possible to naturally turn the steering angle from θAmax to θBmax while suppressing a sudden change in the calculated reaction torque, so that the driver's sense of discomfort is reduced.

After that, when the steering wheel 10 starts to be turned back at time t3, the reaction torque calculator 130 uses the second characteristic corresponding to the vehicle speed B to calculate the reaction torque TR corresponding to the input steering angle θ. Calculate. According to such reaction torque adjustment processing, it is possible to effectively suppress a sudden change in the reaction torque at the end of steering.

2-2. Example of Processing by Steering Control System FIG. 11 is a flowchart showing an outline of processing by the steering control system according to the second embodiment. The processing shown in FIG. 11 is repeatedly executed in each constant cycle in the reaction force torque calculation section 130 of the control device 100 .

In the process of step S200 shown in FIG. 11, it is determined whether or not the "steering end condition" is satisfied. Here, processing similar to that of step S100 is executed. As a result of the determination, if the steering end condition is not satisfied, the process proceeds to step S202. On the other hand, if it is determined that the steering end condition is met, the process proceeds to step S204.

In the process of step S202, similarly to the process of step S108, the reaction force torque calculation process using the second characteristic corresponding to the vehicle speed is executed. When the process of step S202 is completed, this routine ends.

In the process of step S204, it is determined whether or not the vehicle speed has changed. As a result, if the vehicle speed has not changed, the process proceeds to step S202. On the other hand, if the vehicle speed has changed, the process proceeds to the next step S206.

In step S206, the reaction torque TR corresponding to the input steering angle θ is calculated while gradually changing the second characteristic from the characteristic corresponding to the vehicle speed before the change to the characteristic corresponding to the vehicle speed. When the process of step S206 is completed, this routine ends.

As described above, according to the reaction force torque adjustment process shown in FIG. 11, it is possible to suppress abrupt fluctuations in the reaction force torque, which becomes a problem when the vehicle speed changes at the end of the steering. As a result, it is possible to prevent the steering wheel from being abruptly moved, so that the driver's sense of discomfort is reduced.

1 Steering control system 10 Steering wheel 20 Steering shaft 30 Reaction force generator 31 Reaction force motor 40 Steering device 41 Steering motor 42 Reduction gear 43 Steering shaft 51 Steering angle sensor 52 Steering torque sensor 53 Vehicle speed sensor 100 Control device (ECU )
102 processor 104 memory 106 input/output interface 110 steering angle calculator 120 steering angle controller 130 reaction torque calculator 140 reaction torque controller

Claims (5)

A steering control system for a steer-by-wire vehicle,
a steering device for steering wheels of the vehicle by operation of a steering motor;
a reaction force generator that applies a reaction torque to the steering of the vehicle by operating the reaction force motor;
a control device that calculates a steering angle of the wheels for controlling the steering device and a reaction force torque for controlling the reaction force generation device based on the vehicle speed of the vehicle;
The control device is
a turning angle calculation unit that calculates the turning angle according to the steering angle based on a first characteristic representing the relationship between the magnitude of the turning angle and the steering angle of the steering;
a reaction torque calculation unit that calculates the reaction torque corresponding to the steering angle based on a second characteristic representing the relationship between the magnitude of the reaction torque and the steering angle;
The first characteristic and the second characteristic are configured to be adjustable according to the vehicle speed ,
The turning angle calculation unit changes the first characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state in response to the change of the vehicle speed from the first state to the second state. is configured to vary with
When the steering angle is steered to the steering end corresponding to the upper limit of the steering angle, the reaction force torque calculating section calculates the second torque when the vehicle speed changes from the first state to the second state. A steering control system, wherein the two characteristics are maintained as they are in the characteristics corresponding to the first state. After the vehicle speed changes from the first state to the second state at the steering end, the reaction force torque calculation unit calculates the second characteristic when the steering angle is returned to a predetermined steering angle in the third state. 2. A steering control system according to claim 1, characterized in that it is configured to change from a characteristic corresponding to said first state to a characteristic corresponding to said third state. A steering control system for a steer-by-wire vehicle,
a steering device for steering wheels of the vehicle by operation of a steering motor;
a reaction force generator that applies a reaction torque to the steering of the vehicle by operating the reaction force motor;
a control device that calculates a steering angle of the wheels for controlling the steering device and a reaction force torque for controlling the reaction force generation device based on the vehicle speed of the vehicle;
The control device is
a turning angle calculation unit that calculates the turning angle according to the steering angle based on a first characteristic representing the relationship between the magnitude of the turning angle and the steering angle of the steering;
a reaction torque calculation unit that calculates the reaction torque corresponding to the steering angle based on a second characteristic representing the relationship between the magnitude of the reaction torque and the steering angle;
The first characteristic and the second characteristic are configured to be adjustable according to the vehicle speed ,
The turning angle calculation unit changes the first characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state in response to the change of the vehicle speed from the first state to the second state. is configured to vary with
When the steering angle is steered to the steering end corresponding to the upper limit of the steering angle, the reaction force torque calculation unit calculates the vehicle speed when the vehicle speed changes from the first state to the second state. The steering control system is configured to change the second characteristic from the characteristic corresponding to the first state to the characteristic corresponding to the second state at a changing speed slower than the changing speed of . In the second state, the vehicle speed is higher than in the first state,
The turning angle calculation unit is configured to reduce the turning angle with respect to the steering angle when the state of the vehicle changes from the first state to the second state at the steering end. 4. The steering control system according to any one of claims 1 to 3, characterized in that the characteristics are changed. In the second state, the vehicle speed is lower than in the first state,
The steering angle calculation unit is configured to increase the magnitude of the steering angle with respect to the steering angle when the state of the vehicle changes from the first state to the second state at the steering end. 4. The steering control system according to any one of claims 1 to 3, characterized in that the characteristics are changed.

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